Positioning devices are well known in the art, and are used across several technical domains. In the metrology domain, positioning devices are mostly found as rotary encoders, as in WO2006107363A1, or linear encoders as in U.S. Pat. No. 5,563,408. These encoders output a one-dimensional information about the position, and are operating with an excellent resolution—of the order of 1/10 of a micron or of a 1/10,000 of a degree. To reach a positioning with several degrees of freedom, these encoders can be part of a chain, for example in a robotic arm, with the disadvantage that the more encoders are used, the more the positioning resolution degrades. The state of the art of robotic arm positioning system has today a resolution, which is at best one micron. These encoders have in common the fact that the sensing element is measuring the position of a grating with respect to the sensing element. It implies that either the sensing element or the grating is attached to the object the position of which has to be measured.
More elaborate encoders, as disclosed in EP2169357A1, can measure precisely the two dimensional position of a camera with respect to a grating. These encoders are mostly targeted to X-Y positioning tables in the tooling industry, and can achieve sub-micron resolution.
In a different technical field, DE20121855U1 discloses a system to measure the position in space of an object carrying 3 light sources, by measuring the projection of a T-shaped device on a 2D sensitive area. The method suffers 2 major drawbacks: it does not explain how the system can work in a natural environment with several other light sources, and it has a limited precision. Indeed even if it would be possible to build a perfect device with infinite mechanical precision, the resulting measurement precision on the sensitive surface would be at best of the order of the wavelength, i.e. half a micron.
An object of the present invention is to alleviate the limitation of the prior art by disclosing a device that measures the position of one or several light sources in space, with a resolution that exceeds the wavelength by at least one order of magnitude while being robust to external illumination sources. In addition, the present invention is conceived for mass production, and can lead to a very economic system compared to the state of the art.